啤酒生产过程中高级醇形成因素及控制

高级醇是啤酒生产发酵过程形成的,目前可检出的高级醇有30多种.啤酒中高级醇的生成途径主要有氨基酸、α-酮酸途径和糖类物质合成高级醇途径.高级醇的生成与麦汁发酵过程的pH值、α-氨基氮含量、麦汁充氧量、麦汁浓度、发酵强度、酵母菌种及其接种量等因素有关,控制麦汁α-氨基氮含量、可发酵性糖、麦汁充氧量、发酵工艺条件、乙醛含量、酵母菌种及其接种量可有效控制啤酒中的高级醇含量.     

高粱麦汁的α-氨基氮及啤酒的高级醇

在发酵过程中,蜡质高粱麦汁的α-氨基氮及其发酵液中的高级醇含量,可以通过向麦汁中接种普通酵母或接种用酵母-麦芽培养基培养的酵母来进行控制。由蜡质高梁生产的麦汁与普通麦汁的α-氨基氮含量相近。发酵罐顶空的氧浓度由发酵初期的20%,经72小时发酵后,下降到不足1%,这表明:发酵环境逐渐由有氧转变为无氧。两种麦汁产生丙醇、异丁醇、戊醇以及异戊醇所消耗的α-氨基氮量也相近。发酵时间超过144小时后,丙醇、异丁醇、戊醇以及异戊醇的含量变化趋势也相同,异丁醇含量最低。向麦汁中接种用麦汁培养的酵母或添加用酵母-麦芽培养基培养的酵母,分别经过24小时和36小时开始产生丙醇。最终的乙醇和高级醇含量控制在储藏啤酒的要求范围内。用大麦麦芽和蜡质高梁粉生产的麦汁不但可以为啤酒酵母提供充足的营养,而且可以和工业麦汁相比。目前,已经有使用提纯的蜡质高梁粉作为辅料生产储藏啤酒的实例。     

啤酒酿造过程高级醇形成的控制

高级醇是构成啤酒酒体的重要物质 ,淡爽型啤酒中的含量一般控制在50～90mg/L,含量过高 ,则使啤酒产生风味病害。影响高级醇含量的因素有酵母菌种及接种量、麦汁成分和发酵工艺(如发酵温度、发酵方法、发酵度等)。控制方法主要有 :选择高级醇生成量较低的菌种 ,接种量控制在(1.3～1.5)×107个/ml;麦汁中α -氨基氮控制在165～185mg/L,pH在5.2～5.6,溶解氧在8～10mg/L;主酵温度控制在12℃以下 ,控制适当的发酵度     

高梁麦汁的α—氨基氮及啤酒的高级醇

在发酵过程中，蜡质高粱麦汁α－氨基氮及其发酵液中的高级醇含量，可以通过向麦汁中接种普通酵母或接种用酵母－麦芽培养基培养的酵母来进行.控制上蜡质高梁生产的麦汁与普通麦汁的α－氨基氮含量相近。发酵罐顶空的氧浓度由发酵初期的20％。经72小时发酵后，下降到不足1％，这表明：发酵环境逐渐由有氧转变为无氧。两种麦汁产生丙醇，异丁醇，戊醇以及异戊醇所消耗的α－氨基氮量也相近。发酵时间超过144小时后，丙醇，异丁醇，戊醇以及异戊醇的含量变化趋势也相同，异丁醇含量最低。向麦汁中接种用麦汁培养的酵母或添加用酵母－麦芽培养基培养的酵母，分别经过24小时和36小时开始产生丙醇。最终的乙醇和高级醇含量控制在储藏啤酒的要求范围内，用大麦麦芽和蜡质高粱粉生产的麦汁不但可以为啤酒酵母提供充足的营养，而且可以和工业麦汁相比。目前，已经有使用提纯的蜡质高粱粉作为辅料生产储藏啤酒的实例。     

如何降低啤酒中高级醇含量

1高级醇形成的途径(略)2降低啤酒中高级醇含量的措施2.1选用优良的酵母菌种酵母菌种是影响高级醇含量的决定性因素,不同酵母菌种生成高级醇的种类和数量有很大差别。酵母接种量对高级醇的生成量也有一定的影响,当加大酵母接种量时,酵母的繁殖量减少,高级醇的生成量也相应减少,反之,则产生较多的高级醇。2.2合理控制麦汁组分高级醇的生成量随着麦汁浓度的升高而升高。当麦汁中α-氨基酸含量对低时,酵母将通过合成代谢途径生成自身所需的氨基酸,形成较多     

巨峰葡萄酒酿造过程中高级醇生成的研究

葡萄酒中的高级醇为酵母代谢过程产物,是葡萄酒中的主要香味物质。不同接种量、添加不同氮源及葡萄汁含氮量都会影响高级醇的生成量。接种量在6×106个m/L时高级醇生成量较小,葡萄汁中酵母浓度过高或过低都会使高级醇生成量增大。葡萄汁中α-氨基氮总量为180～195m g L/时,杂醇油的生成量较低。添加亮氨酸对高级醇生成量影响最为显著,甘氨酸对高级醇生成量基本无影响。(孙悟)     

不同发酵条件对荔枝酒中高级醇生成的影响

采用4因素3水平的正交试验,分析了影响荔枝酒中高级醇含量的酿造工艺.通过极差分析表明,正交试验4因素中发酵液的α-氨基氮含量对荔枝酒酿造过程中高级醇生成量影响最大,其次是接种量、发酵温度,影响最小的因子是发酵液的初始pH值.荔枝酒发酵中高级醇生成量较少的工艺条件为:α-氨基氮含量为190mg/L,接种量为150 mg/L,发酵温度为15℃,发酵液的初始pH值为3.5.     

高浓高温对啤酒酵母发酵性能的影响

以啤酒酵母S-6为实验菌株,研究了主发酵温度和原麦汁浓度对啤酒发酵的残糖、酒精度、风味物质和絮凝性等性能指标的影响。结果表明,原麦汁浓度一定时,主发酵温度对高级醇和乙酸酯的含量影响较大,主发酵温度由10 ℃提高至16 ℃时,高级醇含量提高了10%～20%,乙酸酯含量提高了8%～16%,但CO2累积质量损失、残糖、酒精度和絮凝性基本不受温度的影响;主发酵温度一定时,原麦汁浓度对酵母絮凝性影响较大,原麦汁浓度越高,酵母絮凝性越低,将高浓（18 °Bx）发酵液稀释50%至常浓（12 °Bx）,残糖、酒精度和高级醇的含量与常浓发酵液基本相同。该研究为选育高温高浓发酵低产高级醇同时强絮凝性酵母菌株提供了重要依据。     

浅析啤酒发酵过程中高级醇的产生及控制措施

通过对啤酒发酵过程中，高级醇形成因素的分析，针对在不同酵母菌株、不同麦汁充氧量、不同麦汁α--氨基氮含量及不同发酵温度的情况下，测定了啤酒中高级醇含量，得出了一些控制啤酒中高级醇含量的结论。     

不同α-氨基氮含量的麦汁对啤酒酵母代谢副产物的影响

该文设计了6个不同α—氨基氮含量的麦汁，在保证其它参数相同的基础上进行了常规发酵试验，整个发酵过程中跟踪检测酵母生长情况、pH、外观糖度、α—氨基氮、双乙酰、高级醇的变化、后酵结束各理化指标。结果证明将麦汁中α—氨基氮含量控制在167mg／L时对控制酵母代谢副产物含量和啤酒风味是最适合的。     

响应面法优化麦汁糖化工艺条件

以大麦芽、小麦芽为原料,麦汁浸出物收得率为评价指标,在单因素试验基础上,利用响应面法对麦汁糖化工艺进行优化研究。结果表明,最佳的糖化工艺为小麦芽添加量为42.0%,水料比为4∶1（mL∶g）,37 ℃投料保温10 min,52 ℃糖化保温45 min,65 ℃糖化保温68 min,78 ℃保温10 min。在此优化糖化工艺条件下,测得麦汁浸出物得率为79.63%,比未优化前提高8.2%。麦汁糖化液中α-氨基酸态氮含量为272.01 mg/L,还原糖含量为9.14 g/100 mL,可溶性氮含量为1.41 g/L。     

乙醛脱氢酶基因过表达酿酒酵母在黄酒中降高级醇作用

为降低黄酒中高级醇产量,以酿酒酵母（Saccharomyces cerevisiae）单倍体菌株AY12α为出发菌,利用同源重组技术构建乙醛脱氢酶基因过表达菌株,并在不同黄酒发酵工艺下探究其对酿酒酵母产高级醇的影响。结果表明,成功构建了5株乙醛脱氢酶基因（ALD2、ALD3、ALD4、ALD5和ALD6）过表达菌株,在大米加麦曲的传统黄酒发酵工艺下,所有改造菌株均可以促进乙酸、降低高级醇的生成,其中改造菌株α-ALD6效果最显著（P＜0.01）,乙酸产量是出发菌AY12α的2.92倍,总高级醇产量下降72.04%。在不同发酵工艺中,改造菌株α-ALD5与α-ALD6均可显著促进乙酸、降低高级醇生成（P＜0.01）;在纯种根霉曲做糖化剂的发酵工艺中,改造菌株在培菌糖化24 h后接入降高级醇效果更好。与纯种根霉曲相比,改造菌株以麦曲作糖化剂时降高级醇效果更好,且改造菌株α-ALD6在大米加麦曲的传统黄酒发酵工艺下降高级醇效果最好。     

发酵条件对啤酒中乙醛及高级醇含量的影响

乙醛及高级醇的含量高是啤酒上头的主要原因.研究了啤酒发酵条件对两者的影响,实验结果表明,适当的提高发酵初期的发酵温度及减少酵母添加量可以有效地降低啤酒中乙醛的含量,而降低麦汁溶氧量和主酵温度可使高级醇含量显著降低.     

桑椹酒酿造过程中高级醇生成的影响因素研究

针对桑椹酒中高级醇含量过高的问题,研究了初始pH值、发酵温度、接种量、SO2添加量、氮源添加量等因素对桑椹酒酿造过程中高级醇生成的影响.试验结果表明:适当增加接种量或降低初始pH值、发酵温度,高级醇生成量明显降低;添加氮源,高级醇生成量增加;在一定范围内,随SO2含量的增加,高级醇生成量增加,当SO2含量达200.00mg/L时,高级醇的生成受到抑制.     

Evaluation of different yeast strains on the quality of beer produced from malted proso millet (Panicum miliaceum L.)

In order to investigate the influence of temperature on pH, alcohol production, carbohydrate profile and aroma compounds, a variety of top-fermenting yeast strains were used to ferment wort obtained from proso millet malt. Champagne (Saccharomyces bayanus), altbier, kölsch and ale (Saccharomyces cerevisiae), as well as Brettanomyces bruxellensis were used in two isothermal (12 and 18 °C) fermentation trials. During the fermentation, changes in pH, extract conversion and the monosaccharide profile were monitored. After 2 weeks of storage, the levels of higher alcohols and esters were also measured in the finished beers. In many cases, a strong resemblance in the behaviour of the selected strains to Saccharomyces was observed during the fermentation. All other influencing fermenting parameters like pitching rate, yeast generation, fermenting vessels geometry, amount of assimilable nitrogen, yeast nutrients, oxygen and CO₂ content and the sugar content were the same for all trials regardless of the yeast applied. However, at higher temperatures Brettanomyces showed more rapid rates of sugar conversion. Concerning the development of aroma components, no uniform picture was evident in these trials, neither with respect to temperature dependence nor to what extent the incurred values are comparable to those already known for beers brewed using barley malt wort. The values for aliphatic alcohols obtained during experimentation, ranged from 23 to 267 μg/L, and the sum of aromatic alcohols, from 2,437 to 11,844 μg/L. Values for ester content were recorded between 188 and 2,543 μg/L. Overall, wort produced using proso millet malt was found to be a substrate that lends itself to alcoholic fermentation, exhibiting a sufficient decrease in pH over the course of fermentation, as well as reasonable alcohol yield and a broad range of aroma components.     

啤酒酵母代谢副产物高级醇的影响因素研究进展

高级醇是啤酒酿造过程中产生的副产物的主要成分，是啤酒的主要香味和口味物质之一。高级醇的生成途径有降解代谢和合成代谢两种。适量的高级醇能赋予啤酒丰满的香味和口味，增加酒体的协调性，但过量存在也是啤酒异杂味的主要来源之一。高级醇含量超过100mg／L会使啤酒口味和受欢迎程度明显降低，啤酒中高级醇含量的标准值为：下面发酵啤酒60～90mg／L；上面发酵啤酒〈100mg／L。高级醇含量主要受酵母菌种、麦汁成分以及发酵工艺条件的影响．因此生产过程应控制好这几个因素。     

低产乙酸啤酒酵母菌株A12的选育及中试

以啤酒酿造生产菌株啤酒酵母JM-36为出发菌株,用甲基磺酸乙酯(EMS)诱变,用含浅蓝菌素的麦芽汁琼脂平板分离抗浅蓝菌素的突变株,在低温下发酵,以发酵液的乙酸、双乙酰、乙醛、高级醇、发酵度和凝聚性为筛选指标,得到1株发酵特性优良的菌株A12。以13°BX麦芽汁为培养基,用100L发酵罐在10℃下发酵14d,菌株A12发酵液的发酵度为68.2%,乙酸、双乙酰、乙醛和高级醇的含量分别为62.3mg/L、0.081mg/L、5.321mg/L和76.43mg/L。菌株A12的主要发酵特性优良且稳定,啤酒口感良好。     

Alpha Amino Nitrogen and Fusel Alcohols of Sorghum Worts Fermented into Lager Beer

The levels of alpha amino nitrogen (AAN) and fusel alcohols during fermentations of lager worts produced from waxy sorghum grits either inoculated with yeast cultured in wort or yeast-malt media were performed. Worts produced from waxy sorghum grits had comparable AAN to commercial wort. The oxygen concentration in the reactor headspace changed from 20% at the beginning of fermentation to less than 1% after 72 hrs fermentation indicating a gradual change from aerobic to anaerobic conditions. The utilization of AAN for production of propanol, isobutanol and amyl-isoamyl alcohols from waxy sorghum grits was comparable to a control wort. Production of propanol, isobutanol and amyl-isoamyl alcohols followed the same trend over 144 hr fermentation. Isobutanol was produced in the lowest concentration. The initiation of propanol production occurred after 24 and 36 hr fermentation for worts inoculated with yeast cultured in wort and yeast-malt media, respectively. The final concentration of ethanol and fusel alcohols were within the expected range found in commercial beers. Worts produced from barley malt and waxy sorghum grits were an adequate substrate for Saccharomyces cerevisiae, and were comparable to a commercial wort. The utilisation of refined waxy sorghum grits as brewing adjuncts for lager beers was demonstrated.     

SIMULTANEOUS ASSESSMENT OF CHANGES OCCURRING DURING BATCH FERMENTATION

Detailed study of the fermentation of wort by Saccheromyces cerevisiae on a pilot scale showed that all the oxygen and considerable quantities of certain amino acids present in the wort were absorbed by the yeast before active fermentation commenced. The pH fell rapidly after pitching and reached a constant level after 32 hr. The α acids and iso α acids in the wort diminished in parallel with the decrease in pH and the increase in concentration of suspended yeast, respectively. Esters and higher alcohols appeared as the carbohydrate content of the wort diminished. Their production did not parallel the uptake of amino acids or changes in the amount of suspended yeast. The level of diacetyl reached a maximum when valine was fully taken up from the wort. Distillation of fermenting wort caused production of diacetyl.